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This invention relates generally to disposable containers and specifically to an insulated disposable cup or container and a method of manufacture.
There are three main types of disposable cups now in use: polystyrene, expanded polystyrene, and paper.
Polystyrene cups are aesthetically pleasing, but they do not provide much insulation and therefore are only used for holding cold drinks. Further they are not biodegradable or easily recycled. Condensation forms on the outside of these cups when holding a cold drink, making the cup wet, cold, and uncomfortable to use for prolonged periods of time. Also the condensation makes the cup slippery and difficult to hold.
Cups made from expanded polystyrene (EPS), and sold under the trademark Styrofoam, are excellent thermal insulators, so that they can maintain the temperature of a drink, whether hot or cold, for long periods of time. They are inexpensive and comfortable to handle because their exteriors stay close to ambient temperature, regardless of the temperature of the drink. However, they are environmentally unfriendly because they are not biodegradable or easily recyclable. As a result, their use has been banned in some municipalities. Also, in order to print these types of cups, a slow and costly printing process must be used, because the cups must be printed after they have been formed, and their rough surface does not allow high-resolution printing.
Standard single-wall paper cups are recyclable and biodegradable and therefore more environmentally sound. However they are poor thermal insulators, so that a beverage in a paper cup quickly warms (if cold) or cools (if hot). They are also uncomfortable to handle because a hot or cold drink can burn or uncomfortably cool a hand. Also, as with the polystyrene cups, a cold drink will cause condensation to appear on the outside, making a paper cup slippery, and difficult to hold. Their single-wall construction makes them fragile, so that large cups filled with liquid may crumble after prolonged handling.
Paper cups also have a greater propensity to leak at the side seam after prolonged periods of holding liquid. This is due to the fact that once the cup""s sidewall blank has been cut from a larger sheet, the cut edges do not have a waterproof barrier on them. Therefore when the cup is formed, the cut edge of the blank at the overlapping side seamxe2x80x94a raw edgexe2x80x94is exposed to the liquid inside the cup. After prolong periods of time, the liquid will wick into the paper through this raw edge. The liquid will then migrate down the side seam and through the bottom of the cup. All existing paper cups have this raw edge and potential leaking problem.
Multi-layered paper cups have been designed to provide thermal insulation and increased strength. U.S. Pat. Nos. 3,908,523 to Shikaya (1975),5,205,473 to Coffin, Sr. (1993), 5,547,124 to Mueller (1996), 5,769,311 to Noriko et al. (1998), and 5,775,577 to Titus (1998) show multi-layered paper cups with an inner cup body and a multi-layered insulating wrap. The wrap provides air pockets or space for thermal insulation.
Although strong and thermally efficient, these cups are all expensive and impractical to manufacture because the inner cup body and insulating wrap are formed separately, and then must be assembled together. The outer wrap is formed from separate pieces that are laminated together, again adding additional cost. The extra steps slow the production process and prevent the cups from being made with standard cup-forming machinery.
U.S. Pat. Nos. 5,490,631 to Iioka et al. (1996), 5,725,916 to Ishii et al. (1998), and 5,766,709 to Geddes (1998) show paper cups coated with a foam material for insulation. These cups are also expensive to manufacture because the foam material must be coated on the cup""s outer layer and then activated in order to expand the foam. The activation process is an extra step that slows and increases the expense of the production process. Another major drawback of these cups is that the textured foam surface is not conducive to printing with sharp and crisp graphics. Yet another drawback is that, although these cups are not EPS foam cups, their foam coated exterior wall still has the xe2x80x9clookxe2x80x9d and xe2x80x9cfeelxe2x80x9d of foam cups, which has a negative impact on consumer acceptance.
Although the cups of the above Sadlier, and Varano and Sadlier patents are a major improvement over existing cups, I have discovered that both the cups and the manufacturing processes by which they are made can be improved.
Accordingly, several objects and advantages of the invention are to provide a cup which (i) has improved thermal insulating properties, (ii) uses less costly materials, (iii) is leak resistant, (iv) can be formed more easily on existing cup machinery through the placement of adhesive, (v) has a surface that is conducive to printing with sharp and crisp graphics, and (vi) has an exterior wall which does not have the undesirable look and feel of foam cups, thereby providing good consumer acceptance.
Further objects and advantages will be apparent from a consideration of the ensuing description and accompanying drawings.
In accordance with one embodiment of the invention, a thermally insulated cup is formed from a sidewall blank having two panels, connected along a common fold score, and a separate insulating sheet. The insulating sheet is adhesively attached to one of the panels of the sidewall blank. Adhesive is applied to an area adjacent to the fold score. The sidewall blank is then folded in half along the fold score, such that the insulating sheet is sandwiched between the two panels, thereby creating a three-layered cup blank. The adhesive which was applied adjacent the fold score bonds the two panels together at that area. The three-layered cup blank is then wrapped or bent around a mandrel and sealed at the overlapping edges. A separate bottom is sealed to the inner layer and the top of the inner layer is rolled radially outward to form a rim. To reduce the thickness of the seam, the blank is thinned in the area adjacent a fold score prior to wrapping.